Cerebral palsy (CP) refers to a group of permanent and non-progressive movement and posture disorders, which are the most common developmental neuro-motor disabilities of childhood affecting about 2-3 per 1000 births. More than 50% of children with CP cannot walk independently and have to use assistive devices such as walkers or wheelchairs. Head trauma or asphyxia during birth are known causes of CP, but what is generally not known is that these factors are present in less than 10% of all CP cases. Thus, the etiology of the majority of cases remains unexplained and it is important to discover additional preventable CP risk factors. We recently found that prenatal exposure to perfluorinated chemicals, persistent organic pollutants that are potential endocrine disruptors, are associated with increased CP risk in a dose-dependent manner in the Danish National Birth Cohort. Many pesticide compounds have developmental neurotoxic effects and/or endocrine disrupting properties, and to our knowledge no published study to date has examined the possible effects of early life pesticide exposure and the risk of CP. Our proposed study is novel and will be the largest population-based study of cerebral palsy and pesticides to date. We will use records from the California Department of Developmental Services (DDS) up to 2010 to identify children that were born 1995-2007 and diagnosed with CP in California. We expect to identify ~10,000 CP cases and will randomly select 1:10 matched controls from the California birth certificates for each CP case. Ambient pesticide exposure estimates pre-pregnancy, during pregnancy and/or first year of life for each child will be estimated using a Geographic Information System (GIS) model we previously developed that links residential addresses at delivery as reported on birth certificates to the California Pesticide Use Reporting (PUR) system. The PUR system contains information on the type, date, and location of all agricultural pesticide applications since 1974 in California. Our GIS model using PUR and land-use maps is the most sophisticated system of its kind and allows specific and detailed pesticide exposure assessment using records which avoids recall bias and to examine specific vulnerable periods in pregnancy (trimesters or months of pregnancy). The diversity of agricultural activities, large amounts and variety of pesticides used in California allow us to examine specific pesticides and their combinations. This project will increase our knowledge of the role environmental toxins play in fetal brain development and will advance scientific insights into CP disease etiology. Our ultimate goal is to improve primary prevention strategies for these severe neurodevelopmental disorders that have lifelong impacts on the quality of life of the patients and caregivers and are great public health burden. The results from this pilot project will also be critical for future applications to examine environmental hypotheses possibly using biomarkers approaches and active data collection.